I need to calculate penalty of Rs250 for each cancelled policies. I base their reference numbers to do this.But some reference numbers are repeated & I should do the above calculation excluding those repeated numbers.In other words, Rs 250 to be charged only against one reference number. Here the reference numbers are dimension & the related premium value due to these reference numbers too are assigned which is a expression. To make this clear, I may present my case as below:

Ref_Number Class Policy_Number Premium(Rs)

RA000C125 MC RA1C 500

RA000C125 MC RA1C 250

RA000C128 FR RA1D 320

RA000C150 FR RA1K 250

EM000C200 MC EM1A 100

EM000C300 FR EM1B 200

EM000C200 MC EM1A 50

I have written expression as follows!

sum({<Ref_Number={'MC'}>}250)

As per above, Rs 250 is calculatedtwice on RA000125, EM000C200 Ref numbers. Help me to avoid this by having included some logic in to my above set analysis.